kvm/powerpc: Add new ioctl to retreive server MMU infos

This is necessary for qemu to be able to pass the right information
to the guest, such as the supported page sizes and corresponding
encodings in the SLB and hash table, which can vary depending
on the processor type, the type of KVM used (PR vs HV) and the
version of KVM

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
[agraf: fix compilation on hv, adjust for newer ioctl numbers]
Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 70 insertions, 0 deletions

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index eb62761b768..930126698a0 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1860,6 +1860,76 @@ See KVM_GET_PIT2 for details on struct kvm_pit_state2.
 This IOCTL replaces the obsolete KVM_SET_PIT.
 
 
+4.74 KVM_PPC_GET_SMMU_INFO
+
+Capability: KVM_CAP_PPC_GET_SMMU_INFO
+Architectures: powerpc
+Type: vm ioctl
+Parameters: None
+Returns: 0 on success, -1 on error
+
+This populates and returns a structure describing the features of
+the "Server" class MMU emulation supported by KVM.
+This can in turn be used by userspace to generate the appropariate
+device-tree properties for the guest operating system.
+
+The structure contains some global informations, followed by an
+array of supported segment page sizes:
+
+      struct kvm_ppc_smmu_info {
+             __u64 flags;
+             __u32 slb_size;
+             __u32 pad;
+             struct kvm_ppc_one_seg_page_size sps[KVM_PPC_PAGE_SIZES_MAX_SZ];
+      };
+
+The supported flags are:
+
+    - KVM_PPC_PAGE_SIZES_REAL:
+        When that flag is set, guest page sizes must "fit" the backing
+        store page sizes. When not set, any page size in the list can
+        be used regardless of how they are backed by userspace.
+
+    - KVM_PPC_1T_SEGMENTS
+        The emulated MMU supports 1T segments in addition to the
+        standard 256M ones.
+
+The "slb_size" field indicates how many SLB entries are supported
+
+The "sps" array contains 8 entries indicating the supported base
+page sizes for a segment in increasing order. Each entry is defined
+as follow:
+
+   struct kvm_ppc_one_seg_page_size {
+        __u32 page_shift;       /* Base page shift of segment (or 0) */
+        __u32 slb_enc;          /* SLB encoding for BookS */
+        struct kvm_ppc_one_page_size enc[KVM_PPC_PAGE_SIZES_MAX_SZ];
+   };
+
+An entry with a "page_shift" of 0 is unused. Because the array is
+organized in increasing order, a lookup can stop when encoutering
+such an entry.
+
+The "slb_enc" field provides the encoding to use in the SLB for the
+page size. The bits are in positions such as the value can directly
+be OR'ed into the "vsid" argument of the slbmte instruction.
+
+The "enc" array is a list which for each of those segment base page
+size provides the list of supported actual page sizes (which can be
+only larger or equal to the base page size), along with the
+corresponding encoding in the hash PTE. Similarily, the array is
+8 entries sorted by increasing sizes and an entry with a "0" shift
+is an empty entry and a terminator:
+
+   struct kvm_ppc_one_page_size {
+        __u32 page_shift;       /* Page shift (or 0) */
+        __u32 pte_enc;          /* Encoding in the HPTE (>>12) */
+   };
+
+The "pte_enc" field provides a value that can OR'ed into the hash
+PTE's RPN field (ie, it needs to be shifted left by 12 to OR it
+into the hash PTE second double word).
+
 5. The kvm_run structure
 ------------------------